Squirrel Vertigo?
We have about 4-6 regulars who come to our feed dish along with the birds, one of which I've named Wobbly.
Wobbly lives up to the name with severe balance problems that cause it to fall over when it runs or sits up to eat, and if it falls over while eating, it'll give up and lie there until it's finished the snack and wants another. It can't climb at all.
It's been coming around for a few weeks and doesn't express any rabid behavior or aggression towards the other squirrels, and they don't try to drive it away, so should I just assume that it is what it looks like, maybe an old head injury? Despite its wobblyness, it's still fast enough that it would take a trap to catch, and I don't want to scare it like that if it's not something that actively needs to be treated.